Back Electromotive Force Analysis of Outer-Rotor Hybrid Excitation Flux Switching Motor

Abstract

Outer-rotor machine installed for in-wheel drive electric vehicles becomes trending nowadays. Previously, outerrotor hybrid excitation flux switching motor (OR-HEFSM) in wheel drive has been proposed to eliminate the transmission gear conventionally used in single drive electric vehicles. However, the back EMF of existing OR-HEFSM is not purely sinusoidal waveform due to harmonic content and high level of cogging torque. This kind of problem might be lead to create noise and tremor in the motor. In this paper, rotor pole skewing technique is adopted to improve back EMF waveform, harmonic content and cogging torque. The analyses carried out based on 2D FEA and 3D FEA using JMAG Designer Version 14.0. Besides, the flux linkage, flux distribution and output performances are also investigated. The results obtained show that the skewing method has improved the back-EMF waveform and reduce the cogging torque. The 3D FEA result indicates the peak to peak value of cogging torque has reduced by 91.42% with skewed rotor method. The torque and power performance of 3D-FEA has maximum values of 248.33Nm with 44.42% and 162.79kW with 33.42%, respectively in which higher when compared with 2D-FEA and skewing.